Add cloudtaf framework

[ta/cloudtaf.git] / libraries / cluster / metasingleton.py

diff --git a/libraries/cluster/metasingleton.py b/libraries/cluster/metasingleton.py
new file mode 100644 (file)
index 0000000..54e832e
--- /dev/null
+++ b/libraries/cluster/metasingleton.py
@@ -0,0 +1,28 @@
+# Copyright 2019 Nokia
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class MetaSingleton(type):
+    instance_attr = '__instance'
+
+    def __call__(cls, *args, **kwargs):
+        if MetaSingleton.instance_attr not in cls.__dict__:
+            setattr(cls,
+                    MetaSingleton.instance_attr,
+                    super(MetaSingleton, cls).__call__(*args, **kwargs))
+        return getattr(cls, MetaSingleton.instance_attr)
+
+    def clear(cls):
+        if MetaSingleton.instance_attr in cls.__dict__:
+            delattr(cls, MetaSingleton.instance_attr)